The pleasant flavour and superior texture are the two major characteristics of chocolate. Chocolate must be solid in room temperature, and yet melt rapidly in the mouth at 37° C. to give the smooth mouth feeling. Dark chocolate, milk chocolate and white chocolate are the three major flavours.
Chocolate is often used as a coating in the food industry. The inventors have investigated means for reducing the calorific value of the chocolate but without reducing the sensory experience provided by the chocolate coating.
Aerated or foamed chocolate are well known products on the market. Examples are Nestle aero, and Mars Skye bar. The main methods for the manufacturing of aerated chocolate are that (1) gas is mixed there into by dissolving under high pressure then the quickly released gas cells can be locked in the solid chocolate matrix; (2) The molten chocolate is continuously stirred to foam followed by cooling, so called whipped chocolate (EP 1 166 639 A1).
In the first method, the gases such as air or carbon dioxide, can be dissolved in molten chocolate under high pressure with or without the help of stirring. After depressurisation, the dissolved gas will come out to form gas cells in the chocolate, and these gas cells will be locked in the chocolate matrix if the temperature is quickly cooled down below the melting temperature of chocolate during the depressurisation process. The solidified chocolate will keep the gas cells and stabilise the prepared chocolate foam. However, the gas cells are normally big and the aeration is not easy to control. If the chocolate is above its melting temperature, the chocolate foam is not stable and thus the coating, dipping and rolling which are common for chocolate application, can not be applied to the chocolate foam prepared by this method.
In any case, it has been observed that aerated chocolate is lighter in colour than unaerated chocolate, and this may be perceived by the consumer as chocolate which is ‘milkier’ and therefore not containing a high level of cocoa. Depending on the context, this may give an impression of reduced quality chocolate. As the degree of aeration increases, so to does the lightening of the chocolate.
This problem has been recognised for a long time and WO0115543 describes a process for coating a food product comprises applying a coating of aerated liquid confectionery material and applying on top of this another coating or relatively unaerated liquid confectionery material to improve the colour of the item. Apart form the fact that it requires a two step process, it also tends to defeat the purpose of using aerated chocolate since it requires adding unaerated chocolate on top.
It has now been found that it is possible to aerate chocolate while preserving its colour by adding a carefully selected pigment.
Tests and Definitions
Sucrose Esters
Sucrose esters of fatty acids can be obtained by esterifying one or more of the hydroxyl group of a sucrose molecule with fatty acids. The fatty acids react with one or more hydroxyl groups to form mono, di, tri or multi-fatty acid ester, or mixture thereof. Preferably the sucrose ester emulsifier comprises a mixed ester or homo-ester. The fatty acid is preferably selected from the group consisting of lauric acid, myristic acid, palm itic acid, stearic acid and mixtures thereof.
Chocolate
By the term “chocolate” is meant dark chocolate, milk chocolate, white chocolate, flavoured chocolate, couverture chocolate, compound chocolate (which is made from a combination of cocoa solids, non-cocoa butter vegetable fat and sweeteners) and mixtures thereof. The chocolate may also comprise inclusions such as nuts or pieces thereof, dried fruit, such as raisins, or pieces thereof, biscuit and mixtures thereof. The chocolate must, however, remain substantially anhydrous. By the term “substantially anhydrous” is meant comprising no more than 5%, preferably no more than 3%, more preferably no more than 1% w/w water.
HLB Value
The HLB value is given by the equation HLB=20*Mh/M, where Mh is the molecular mass of the hydrophilic part of the molecule and M is the molecular mass of the whole molecule thus giving a value on an arbitrary scale of 0 to 20.
For fatty acid esters, HLB=20 (1-S/A) where                S=Saponification value        A=Acid number of the fatty acid        
Therefore an HLB value of 0 corresponds to a completely hydrophobic molecule and an HLB value of 20 corresponds to a completely hydrophilic molecule.
Typical HLB values are:                0 to 3 an anti-foaming agent        4 to 6 a water-in-oil emulsifier        7 to 9 a wetting agent        8 to 18 an oil-in-water emulsifier        13 to 15 a detergent        10 to 18 a solubiliser or a hydrotrope        
Optical Microscopy
Optical microscopy was used to measure the bubble morphology in the aerated chocolate. The samples were placed on a glass slide and covered with a cover slip. The optical images were taken on a Polyvar microscope (Reichert-Jung Limited). For the morphological study of foams, a 200 μm spacer was used between the slide and cover slip to protect the bubble from deformation.
Scanning Electron Microscopy
Aerated chocolates were prepared for cryo-scanning electron microscopy by cooling it immediately after preparation to 50 degrees centigrade and placing it on a 10 mm diameter aluminium sample holder drilled with a 5 mm diameter depression. The sample holder was then immediately plunged into nitrogen slush, transferred to a Gatan Alto 2500 low temperature preparation chamber and warmed to −90 degrees centigrade for fracture and coating with 2 nm Au/Pd. The coated sample was then transferred to a Jeol 6301F field emission scanning electron microscope fitted with a Gatan cold stage and examined at −150 degrees centigrade. Images were obtained at 5 kV.